Mitogen-activated protein kinase (MAPK) pathways mediate signals which control diverse cellular processes including growth, differentiation, migration, proliferation and apoptosis. One MAPK pathway, the extracellular signal-regulated kinase (ERK) signaling pathway, is often found to be up-regulated in tumors. Pathway members, therefore, represent attractive blockade targets in the development of cancer therapies (Kohno and Pouyssegur, 2006). For example, U.S. Pat. No. 7,354,939 B2 discloses, inter alia, compounds effective as inhibitors of ERK protein kinase. One of these compounds, 4-(5-Chloro-2-isopropylaminopyridin-4-yl)-1H-pyrrole-2-carboxylic acid [1-(3-chlorophenyl)-2-hydroxyethyl]amide, is a compound according to formula (I):

Pharmaceutical compositions are often formulated with a crystalline solid of the active pharmaceutical ingredient (API). The specific crystalline form of the API can have significant effects on properties such as stability and solubility/bioavailability. Instability and solubility characteristics can limit the ability to formulate a composition with an adequate shelf life or to effectively deliver a desired amount of a drug over a given time frame. One strategy used to achieve the desired physical parameters is the practice of salt selection. (Peterson et al., 2006).
There exists an unmet need for crystalline forms of 4-(5-Chloro-2-isopropylaminopyridin-4-yl)-1H-pyrrole-2-carboxylic acid [1-(3-chlorophenyl)-2-hydroxyethyl]amide which exhibit improved properties for formulation of pharmaceutical compositions. The present application is directed to meeting this and other needs.